1. Field of the Invention
The present invention relates generally to electronics cooling systems and more specifically it relates to a sealed spray cooling system for reducing coolant loss within thermal management systems.
2. Description of the Related Art
Thermal management systems for electronic systems have been in use for years. Thermal management systems are used in various applications such as but not limited to semiconductor burn-in, server computers, personal computers and workstations, rack mount servers, diagnostics, and large telecommunications and computing facilities. Conventional thermal management systems utilized today are comprised of, for example, either air-cooled enclosures, or fluid-cooled cold plates. Upcoming technologies include refrigeration systems or other two-phase based technologies.
Modern electronic devices have increased thermal management requirements. Spray cooling is being adopted today as the most efficient option for thermally managing electronic systems. U.S. Pat. No. 5,220,804 entitled High Heat Flux Evaporative Spray Cooling to Tilton et al. describes the earlier versions of spray cooling technology. U.S. Pat. No. 6,108,201 entitled Fluid Control Apparatus and Method for Spray Cooling to Tilton et al. also describes the usage of spray cooling technology to cool a printed circuit board. Spray cooling may be performed locally (i.e. where the chip is sprayed directly), globally (i.e. where the chip and surrounding electronics/boards are also sprayed), a combination of locally and globally, or in conjunction with air cooling or other cooling methods.
Various methods of spray cooling thermal management may be employed for semiconductors and other electronic devices. For adequately low heat fluxes, it may be appropriate to cool the electronic devices through purely forced convection (i.e. no effective evaporation of the coolant occurs). For intermediate heat fluxes, it may be appropriate to utilize a combination of forced convection and phase change heat transfer (i.e. the latter method resulting in evaporation of the coolant). For the highest level of heat fluxes, it may be appropriate to optimize purely on phase change heat transfer. Expensive dielectric coolants are commonly utilized liquid coolants in spray cooling thermal management systems today, thereby making vapor recovery increasingly important.
For cold plates that are in direct contact with the electronic devices being cooled, it is of paramount importance that the cold plate makes uniform contact with the device. For a given device, non-uniform contact leads to elevated junction temperatures, and large thermal gradients across the device. For an application such as the burn-in of multiple semiconductor devices, such non-uniform contact also creates unacceptable thermal gradients across the batch (leads to large junction temperature spread). Current equipment employs actuation systems that place the cold plates in physical contact with the devices to be cooled. To ensure uniform contact between the cold plates and devices, the actuation systems employ gimbaling mechanisms that allow the cold plate to float on a sort of ball and socket joint, and that allow it to seat relatively well. Specific embodiments of the present invention are highly tolerant of poor seating which negates the need for the expensive and cumbersome gimbaling mechanisms. The vacuum maintained within the spray cavity ensures that if a seal structure is not well seated, there is no danger of additional coolant loss.
In most spray cooling applications, a certain volume of coolant is changed to vapor. When the equipment being cooled needs to be accessed, for example, for maintenance, there is the chance that such vapor could be lost to the atmosphere. In a burn-in application, it is critical to rapidly remove the burn-in boards to reduce costly equipment downtime. Another example is the thermal management of servers employed in data centers, wherein the processors or entire servers may need to be removed for maintenance. In any application of spray cooling thermal management, coolant vapor loss is a significant issue. Hence, there is a need for technology that will mitigate the volume of coolant loss in a spray cooling thermal management system.
While conventional thermal management systems may be suitable for the particular purpose to which they address, they are not as suitable for reducing coolant loss. Conventional spray cooling thermal management systems may have significant coolant vapor loss, which would increase the thermal management costs.
In these respects, the sealed spray cooling system according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in so doing provides a system primarily developed for the purpose of reducing coolant loss within thermal management systems.